Abstract

Pseudomorphs of cryogenic fissures in stratified medium to fine silty sand and sand at Belchatów, Poland, indicate both epigenetic and syngenetic freezing of sediments at various times during the Pleistocene. Syngenetic fissures are more frequent. They are typically 0.5–2.0 m in vertical dimension, range in width from 5 to 20 cm, exhibit both upwarps and downwarps of enclosing sediments, and are offset from each other in the stratigraphic sequence. Epigenetic fissures are larger, generally increase in width upwards, and are related to an inferred ground surface. It is difficult to distinguish between syngenetic fissures that penetrate permafrost and soil (ground) veins or wedges that require only deep seasonal frost for their formation. Cold, continental environments characterized by rapid sedimentation and permafrost aggradation appear most conducive for formation of syngenetic fissures. Today, both large and small syngenetic fissures are known to exist in the permafrost regions of Siberia but are rarely reported from the western Arctic lowlands of North America.

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